Drawing ASTs for expressions: Correct Solution

For each of the Java expressions below:

• Draw an AST for the expression.
• Show how the expression evaluates at each node in the tree.

Be sure that your tree accurately reflects how Java would evaluate the expression.

Part 1

Given the following variables:

double e = 5.0;
double broa = 4.0;
double shoenlod = 5.0;
double sint = 4.0;
int gispe = 9;

...draw the AST and evaluation results for the following expression:

1 - 0 - e / broa / shoenlod / sint + gispe

Solution

Things to double-check in your solution:

• Do you have the left and right branches on the correct side?
• Did you indicate the difference between ints and floating point values?

Part 2

Given the following variables:

double vube = 2.0;
boolean ceen = false;
double qabed = 5.0;
int u = 4;
boolean peshsprom = false;

...draw the AST and evaluation results for the following expression:

!(5 >= vube) == 2 > 9 && (ceen == (qabed != u) == peshsprom) != 8 <= 0

Solution

Things to double-check in your solution:

• Does your tree correctly reflect the precedence of && and ||?
• Did you correctly show short-circuiting? (That is when the right branch of && or || is never evaluated because the left branch already determines the answer.)

Part 3

Draw the AST and evaluation results for the following expression:

0 + 1 + "2" + "3" + 4 + 5 + 6 + 7

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

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